Transcript Mollusca
Phylum Mollusca Phylum Mollusca Mollusks are soft-bodied animals that usually have an internal or external shell. Mollusks include: - Snails - Slugs - Clams - Squids - Octopus Mollusca Characteristics Soft body External or internal shellMuscular foot and visceral mass (covered by mantle) Radula in some-used to scrape food Bilateral symmetry No segments Coelomates Open circulatory system- blood not always in a vessel Trochophore larvae Trochophore larvapaddlelike, bristles Apical tuft Stomach Ciliary band Mouth Anus 4 Phylum Mollusca: Anatomy The body plan of most have 4 parts: mantle, shell, visceral mass, and foot. 1.The mantle is a thin layer of tissue that covers most of the mollusk’s body like a cloak. Phylum Mollusca: Anatomy 2. The shell is made by glands in the mantle that secretes calcium carbonate. -- Reduced or lost in slugs -- Internal or lost in Cephalopods (squid/octopus) Phylum Mollusca: Anatomy 3. Visceral mass is just beneath the mantle and consists of the internal organs. Phylum Mollusca: Anatomy 4. The muscular foot takes many forms, including flat structures for crawling, spadeshaped for burrowing, and tentacles for capturing food. Phylum Mollusca: Feeding Mollusks have a radula: a rough, tongue-like organ with rows of teeth like structures. Some use it to scrape algae off surfaces, and other use it to rasp up flesh from prey. Body Systems • • Muscular-Skeletal - outer shell, soft body, muscular foot for movement. Digestion food brought in through a siphon system mouthdigestive gland intestineanus. Nervous- A Mollusk has no formal nervous system, but has a series of ganglia that conduct impulses. Circulatory - heart, blood and blood vessels. Respiratory- tubes called siphons- bring water in and out of their bodies to take in oxygen and give off carbon dioxide. gills- help with this. Reproductive- separate males or female and reproduces sexual- with a large gonad. Excretion- nephridium that gets rid of wastes anus Classes of Mollusks There are 8 classes of Mollusks (Covering 5) Class Monoplacophora: placo=-plate Class Polyplacophora: Chiton Class Gastropoda: snails, slugs, & sea hares Class Bivalvia: clams, oysters, mussles & scallops Class Cephalopoda: octopus, squids, cuttlefish, Class Monoplacophora Mono= one Placo=plate Phora= to have or bear Mollusks with a single, curved shell Marine Thought to be extinct until one was found in 1952 Class Polyplacophora Poly = many placo= plates shell is divided into 8 curved plates or shells Marine Have a reduced head and a flattened foot Ex. Chiton Polyplacophora When disturbed, the edges of the mantle tightly grip the substrate creating a powerful vacuum that holds the chiton in place Has the ability to roll into a ball when dislodged Class Bivalvia Clams, Oysters, Mussels & Scallops Live in water, filter feeding 2 shells held together by powerful muscles(hinges) No radula Hatchet shaped foot for burrowing Class Bivalvia only Mollusks that don’t have a radula Feed by siphoning and filtering large particles from water Can survive for short times out of water by closing their valves Scallops can move around by flapping their shells when threatened. Class Bivalvia Oyster Catcher Willet Plover Starfish, many sea birds (Oyster Catchers, willets, plovers, and much more), and walrus feed on them • The largest bivalve is the Giant Clam Can weigh more than 450 lbs http://www.arkive.org/giant-clam/tridacnagigas/video-00.html Class Bivalvia: Making Pearls Oysters filter-feed An irritant, such as a grain of sand, becomes embedded in the mantle. The animal coats the irritant with the same material used to produce the lining of its shell called motherof-pearl. The coating makes the irritant less painful. It continues to coat the irritant, creating a pearl. Class Bivalvia Bivalves are filter feeders valuable service by reducing suspended particles in their habitats If their populations are reduced, their water in that area will become turbid (cloudy) Turbid water reduces light penetration for photosynthesis in sea-grasses and algae Without plants, many other populations of organisms will also decrease Class Bivalvia: Eating Bivalves Mmmmmmm… Mmmmm…. “Oysters on a half-shell” Considered an aphrodisiac Eaten fried, Steamed, or raw GOOD! Class Gastropoda Gastropoda means “stomach foot” Includes snails, slugs, & sea hares Most are single shelled- asymmetrical and coiled Some are shell-less (slugs & sea hares) Radula for scraping food Class Gastropoda They are 2nd only to insects in their number of known species gardens, woodland, deserts, rivers and lakes; estuaries, mudflats, the rocky intertidal, the sandy subtidal, in the depths of the oceans, and many other ecosystems Class Gastropoda They move using a muscular foot Many have 2 or 4 tentacles with eyes on the tip Most have a coiled shell that opens to the right The Lightning Whelk is the only “left handed” snail Class Gastropoda Many have an operculum that is used as a “trap-door” to close the body inside the shell Most breath using gills Class Gastropoda: Importance Many animals feed on gastropods -- Example: Sea otters eat abalone Class Gastropoda Hermit crabs inhabit empty snail shells. When the crab gets too big for the shell, they find a larger one. Hermit crabs have wars for prized shells. http://www.arkive.org/common-hermitcrab/pagurus-bernhardus/video-03.html Class Gastropoda Suborder Nudibranchia - Means “Naked gill” - marine, shell-less gastropods - The gills are arranged as feathery plumes on their backs - Are brightly colored Warning: many are poisonous Camouflage Class Cephalopoda Class Cephalopoda Typically soft-bodied with the head attached to a single foot. The foot is divided into tentacles or arms. Cephalopoda Locomotion Most swim by forcefully expelling water from the mantle cavity through a ventral funnel (Siphon). Swim using jet propulsion method. Funnel can point forward or backward to control direction The force of water expulsion determines speed. Cephalopoda Feeding beaks: similar to a bird’s beak, used for crushing and picking apart food. Beak “Masters of disguise!” -- Color changes are possible due to special pigment cells contained within its skin, called chromatophores. Cephalopoda Chromatophores: small structures filled with colored ink which can be expanded and contracted to communicate with others or as camouflage against the landscape. Cephalopoda Color changes are used for: - Camoflague - Communication (alarm/courtship) - Many are bioluminescent to attract prey and mating partners! Octopus are Highly Intelligent Maze and problem-solving experiments have shown that they do have both short- and longterm memory. Can be trained to distinguish between different shapes & patterns Observed having observational skills Class Cephalopoda Octopus: - Have 8 arms - Arms have sucking disks that grab & hold prey. - Blood is pale blue. - The shell is absent! Class Cephalopoda More Octopus: - When female lays eggs, she stops eating, & protects her eggs until she dies. Class Cephalopoda Blue-ringed Octopus: - The most toxic - A bite is nearly always fatal to humans. Giant Octopus: - - Can weigh 600 lbs Known to attack ROV and bite into metal Class Cephalopoda • People eat octopus: Dead or ALIVE! • A dish called “San Nakti” means “living octopus” -- Kind of difficult to get the octopus down because the tentacles stick to your mouth and throat. -- They also have a tendency to walk off your plate! Hungry? Hungry? Cuttlefish & Squid Have 10 appendages (decapods): 8 arms with suckers and 2 long retractile tentacles Forms of Cephalopoda Cuttlefish: -- Have an internal gas filled “bone” that helps with buoyancy called the cuttlebone. -- Well, it is not for sharpening the beak. It's amazing how many pet owners think this is its purpose. Cuttlebone is provided to birds as a source of calcium and other necessary minerals. It is especially important to breeding hens. Forms of Cephalopoda Squid: -- Color changes reflect the animal’s mood. -- Messages: ready to mate, sexual identification, alarm, ready to hunt, & hiding. Cephalopoda: Squid Squid: Most of the shell has disappeared, leaving only a thin, horny strip called a pen which is enclosed in the mantle. Cephalopoda Squid: Giant Squid are the largest invertebrate Have the largest eyes in the animal kingdom Never been seen alive!!! Their bodies wash up onto beaches Sperm whales feed on giant squid Giant Squid Forms of Cephalopoda Nautilus Forms of Cephalopoda Nautilus -- Sticking out from the shell is the nautiluses’ arms and a leathery hood that closes the animal into its shell for protection. -- This nautilus has more than 90 arms. Forms of Cephalopoda More Nautilus: -- The only cephalopod encased in a shell. -- The nautilus can fill the chambers it doesn’t occupy with gas or water. If the chambers are filled with gas, the animal will float. If the chambers are filled with water, the animal will sink. Forms of Cephalopoda More Nautilus: -- The living animal inhabits only the last chamber. -- As it grows, it moves forward, secreting behind it a new septum. -- The chambers are connected by a cord of living tissue called a siphuncle, which extends from the visceral mass. Nautilus Table 1 Classes of the Phylum Mollusk Pronu Commo # Scientific Name nciatio Foot n Name Shells n Polyplacophore 8chitons [Amphineura] plates Monoplacophore 1 s Gastropoda Bivalvia [Pelecapoda] Celphalopoda GAS- univalves 1 or troh- (snails, none pahdz slugs) bivalves 2 # of Species ~650 ? extinct stomach ~90,000 foot hatchet foot SEHFoctopus, interna head uh-lohsquids l foot pahdz ~8000 ~650 Polyplacophore (many plates). [Amphineura]. The End of Mollusca